The electronic mail service is one of most widely used Internet services by users. Most portal sites provide an electronic mail service, and a predetermined mail storage space is provided to each user, by which users can store mails in the limited space.
Web mail service provided by portal sites is a service that can read mails through web browser without a particular user interface or a protocol for receiving mails from a mail server. In conventional web mail service, small size storage space for mail was generally provided, however, request for expansion of mail storage space is increasing more and more.
In case of conventional mail service, because a predetermined mail storage space is given to users, new mails cannot be received if the mailbox reaches over the predetermined size. Therefore, users have to delete unnecessary mails to use the mail service continuously. If there are many mails that users want to store for a long time personally and size of these mails is near the predetermined storage size given to users, users have to delete mails although uses want to store them.
In addition, presently, portal sites provide various services that offer storage space for personal information such as blog, personal homepage, these kinds of personal information storage services are becoming more diversified.
Although the personal information storage services are becoming more diversified, no service that can use personal information storage space in a synthetic way has been provided. Therefore, although there is some storage space left in blog or personal homepage, users still have to delete mail data if there is not enough mail storage space, and mail data cannot be stored in another personal information storage space.
Therefore, although various personal information storage spaces are provided, users cannot utilize each of the storage spaces effectively by controlling storage of personal information. Recently, request for expanding mail storage space is increasing more and more, and it is necessary to store mails to be stored for a long period of time without restriction of storage space.